gfx4snes corruption for PNG files with a bit depth of 1

[undisbeliever]

gfx4snes is not converting this PNG file correctly.

Here is the command I am using to convert the file:

gfx4snes -R -s 8 -u 4 -p -t png -i font-2bpp.png

and this is output of a simple Hello World program using consoleInitText() and consoleDrawText().

I also see the same corruption when converting the file to a 4bpp tile format.

The PNG file was created with GIMP, it contains 2 colours in the colourmap and was exported to PNG using the automatic pixel format option.

Loading the PNG file in Aseprite and saving it to a new file causes gfx4snes to work as expected.

This is the output of the same Hello World program using the png file from Aseprite:

Comparing the two png files lead me to believe gfx4snes was unable to correctly load PNG files with bit-depth of 1.

ExifTool Version Number         : 12.76
File Name                       : font-2bpp-gimp.png
Directory                       : .
File Size                       : 542 bytes
File Modification Date/Time     : 2024:04:05 17:14:22+10:00
File Access Date/Time           : 2024:04:05 17:14:22+10:00
File Inode Change Date/Time     : 2024:04:05 17:38:06+10:00
File Permissions                : -r--r--r--
File Type                       : PNG
File Type Extension             : png
MIME Type                       : image/png
Image Width                     : 128
Image Height                    : 48
Bit Depth                       : 1
Color Type                      : Palette
Compression                     : Deflate/Inflate
Filter                          : Adaptive
Interlace                       : Noninterlaced
Palette                         : (Binary data 6 bytes, use -b option to extract)
Image Size                      : 128x48
Megapixels                      : 0.006

ExifTool Version Number         : 12.76
File Name                       : font-2bpp-aseprite.png
Directory                       : .
File Size                       : 773 bytes
File Modification Date/Time     : 2024:04:05 18:20:00+10:00
File Access Date/Time           : 2024:04:05 18:20:00+10:00
File Inode Change Date/Time     : 2024:04:05 18:20:00+10:00
File Permissions                : -r--r--r--
File Type                       : PNG
File Type Extension             : png
MIME Type                       : image/png
Image Width                     : 128
Image Height                    : 48
Bit Depth                       : 8
Color Type                      : Palette
Compression                     : Deflate/Inflate
Filter                          : Adaptive
Interlace                       : Noninterlaced
SRGB Rendering                  : Perceptual
Palette                         : (Binary data 6 bytes, use -b option to extract)
Image Size                      : 128x48
Megapixels                      : 0.006

The following patch fixes gfx4snes for my PNG file. I do not know why pngstate.decoder.color_convert is 0, so I'm writing a bug report instead of submitting a PR.

diff --git a/tools/gfx4snes/src/images.c b/tools/gfx4snes/src/images.c
index c1a1029e..137d2275 100644
--- a/tools/gfx4snes/src/images.c
+++ b/tools/gfx4snes/src/images.c
@@ -106,8 +106,7 @@ void image_load_png(const char *filename, t_image *img, bool isquiet)
     // optionally customize the state
     lodepng_state_init(&pngstate);
 
-    // no conversion of color (to keep palette mode)  
-    pngstate.decoder.color_convert = 0;
+    pngstate.decoder.color_convert = true;
 
 	// always in 8 bits and palette mode
 	pngstate.info_raw.colortype=LCT_PALETTE;

PVSnesLib version: 4.2.0
OS: Linux x64

[alekmaul]

Thanks, I will try this.
But, if I remember well, the color convert also damages the colors.
We will see.